BORDO WIRE GAUGE QUICK SILVER M2 HSS JOBBER DRILLS
118° Split Point (crankshaft point)
Split point is self centering and reduces the need for end thrust. Friction at workpiece is reduced. 118° point angles are ideal for use in materials such as mild steel and cast iron. The 118° point creates easily controlled chips which are wide and thin.
Gauge size drill calculations are generally made utilising a referance book or table. For example, to drill a hole which is 10 thou (thousandth of an inch = .001) bigger than a 1/8″ bolt, the user must first work out that 1/8″ is 125 thou, so the required hole size is 135 thou. Using a reference table establishes that you would need a number 29.
Number drill bit gauge sizes are analogous to, but different from, American wire gauge.
Number gauge is most commonly used from size 80 (the smallest) to size 1 (the largest) followed by letter gauge size A (the smallest) to size Z (the largest). Number gauge is actually defined down to size 97, but these smallest sizes are very rarely used.
DRILL BIT SURFACE TREATMENT
Bright Finish Jobber Drills have no surface treatment and are supplied in the as-ground condition. These tools are suitable for general purpose use, particularly for non-ferrous applications.